Results of the Cancer Research Campaign Adjuvant Trial for Perioperative Cyclophosphamide and Long-Term Tamoxifen in Early Breast Cancer reported at the tenth year of follow-up. Cancer Research Campaign Breast Cancer Trials Group.

Abstract

Over 2,000 patients with early breast cancer were recruited into a trial between 1980 and 1985. This trial was of a factorial 2 x 2 design to investigate the benefits of a short course of perioperative cyclophosphamide or tamoxifen 20 mg daily for 2 years. At the tenth year of follow-up no significant benefit is noted for perioperative cyclophosphamide, however the main effect analysis for adjuvant tamoxifen demonstrates a significant improvement in disease-free survival which increases with time during the follow-up period. These results are in keeping with the World Overview of Trials of Adjuvant Tamoxifen. However, this study is unique, having a large number of node negative patients and over 500 premenopausal women in a comparison of tamoxifen and control. The relative risk reductions for the node negative patients for disease-free survival are greater than for the node positive patients. This might suggest that the absolute benefit for adjuvant tamoxifen is similar in both groups of patients, bearing in mind the increased risk of relapse with the node positive patients. No trend for interaction emerges according to age or menopausal status suggesting an identical benefit for premenopausal women. Of particular interest is the development of contralateral breast cancer. The initial overall effect which emerged at the third year of follow-up ceases to be apparent. However, subgroup analysis according to menopausal status suggests a trend for interaction with a reduction in the risk of contralateral breast cancer in the postmenopausal women and an increase in the risk of contralateral breast cancer in premenopausal women. Plausible mechanisms exist to explain this difference in outcome and these data need to be checked against other large trials of adjuvant tamoxifen at a time when we are considering the chemoprophylaxis of breast cancer in high risk premenopausal women.